Examples of electrolytic capacitors include tantalum capacitors that have a porous anode body, an electrode, and an electrically conductive layer. The anode body is connected to the electrode, which is covered by the electrically conductive layer. The anode body is in contact with the electrode and, along with the electrode, makes up to the anode of the electrolytic capacitor. A multilayered cathode is produced on a surface of the anode body from conductive materials by the following processes, which are performed in order: dipping, drying and pyrolysis.
During dipping, the electrode should not come into contact with solutions, suspensions, dispersions and lacquers, i.e., the electrode should not become wet. This is because liquid on the electrode forms a hard deposit on the electrode. This hard deposit adversely affects the electrical characteristics of the resulting capacitor.
It is noted that the electrode can become wet as a result of excessive dipping or as a result of a meniscus formation of liquid used during dipping. The electrode also can become wet via the capillary effect which, in this case, results from channels on a surface of the electrode.
The foregoing hard deposits on the electrode also affect the amount of space the capacitor occupies.
In view of the foregoing, an anti-wetting barrier can be produced on the electrode to prevent the electrode from becoming wet and thereby prevent formation of hard deposits on the electrode. In this regard, the anti-wetting barrier should be placed as closely as possible to the anode body in order to limit and/or prevent the formation of hard deposits.
In electrolytic capacitors, anti-wetting barriers have been used, which include a round wire connected to a capacitor's anode body. The anode body is connected to capacitor electrodes and the round wire is made of a TEFLON® ring spread onto a capacitor electrode before dipping. Such a TEFLON® ring has the disadvantage that it either must be reapplied to the electrode after dipping or it stresses. If the TEFLON® ring remains on the electrode, the TEFLON® ring takes up electrode area and thus increases the size of the capacitor.
A method is known in the prior art, in which a round-wire formed electrode is placed in a continuous stream of fluid anti-wetting agent. An anti-wetting barrier forms on the electrode when the anti-wetting agent dries. This method, however, is not suitable for use with electrodes formed of flat sheet metal. This is because it would require spraying the anti-wetting agent, rather than applying the anti-wetting agent via a continuous stream. As a result, the process becomes uncontrollable.
Furthermore, prior art methods for applying a fluid anti-wetting agent make it difficult to control the amount of anti-wetting agent that is applied. Thus, the volume and/or the space occupied by the anti-wetting barrier are both very difficult to control and to reproduce. Anti-wetting barriers, which are produced according to prior art methods, usually have a width of 500-1000 μm and a height of >10 μm. As a result, such anti-wetting barriers require more space, thereby increasing the size of a resulting electrolytic capacitor.
Furthermore, a protective ring of TEFLON® is technically difficult to achieve with electrodes that are made of flat sheet metal because an oblong slit in the protective ring is necessary.
It is therefore a goal of this application to provide a method for producing an anti-wetting barrier that is relatively small in size.